Method for processing telephony sessions of a network

ABSTRACT

A method for processing telephony sessions of a network including at least one application server and a call router, the method including the steps of assigning a primary Uniform Resource Identifier (URI) and at least a secondary URI to an application; mapping a telephony session to the primary URI; communicating with the application server designated by the primary URI using an application layer protocol; receiving telephony instructions from the application server and processing the telephony instructions with the call router; detecting an application event; and upon detecting the application event, communicating with the application server designated by the secondary URI.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 13/021,645, filed 4 Feb. 2011, the entirety of which isincorporated by reference herein.

TECHNICAL FIELD

This invention relates generally to the telephony field, and morespecifically to a new and useful method for processing telephonysessions in the telephony field.

BACKGROUND

In recent years, telephony applications have become more integrated withweb applications. Telephony platforms have enabled web developers toapply their skill sets in the field of telephony. New products andservices have been offered leveraging this new technical capability.However, integrating web applications with telephony services haveintroduced new problems to the field of telephony. In telephonyapplications, users have higher expectations and application errors arenot expected or tolerated. In a telephone call there is lessopportunities to signal to a user of an error. Companies providingtelephony applications can lose customers during an application error.Additionally, applications are unable to be integrated with a telephonesession. This places an increase burden on developers and limits thecapabilities of telephony applications. Thus, there is a need in thetelephony field to create a new and useful method for processingtelephony sessions. This invention provides such a new and usefulmethod.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic representation of a method of a preferredembodiment of the invention;

FIG. 2 is a schematic representation of a method of a preferredembodiment of the invention with a fallback URI;

FIG. 3 is a schematic representation of a method of a preferredembodiment of the invention with a status callback URI;

FIGS. 4A-4C are examples of a HTTP GET request, a HTTP POST request, anda HTTP GET request, respectively;

FIGS. 4D-4F are examples of a HTTP requests; and

FIGS. 5A and 5B are examples of XML responses.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments of the inventionis not intended to limit the invention to these preferred embodiments,but rather to enable any person skilled in the art to make and use thisinvention.

As shown in FIG. 1, a method for processing telephony sessions of apreferred embodiment includes assigning a primary Uniform ResourceIdentifier (URI) and at least one secondary URI to an application Silo;mapping a telephony session to the primary URI S120; communicating withthe application server designated by the primary URI using anapplication layer protocol S130; receiving telephony instructions fromthe application server and processing the telephony instructions withthe call router S140; detecting an application event S150; and upondetecting the application event, communicating with the applicationserver designated by the secondary URI S160. The method functions toredirect program flow to secondary or backup applications. In oneembodiment the method functions to handle and possibly recover fromerrors that occur during a session of a telephony application, as shownin FIGS. 2A and 2B. For example, when an application error occurs, thesecondary URI may be used as a fallback URI to take control of callcontrol. In a second embodiment, the method functions to enableadditional services to be updated during a call. For example, an outsideservice may store and process phone call recordings, and anytime arecording occurs on a telephony platform, the recording is sent to theoutside service located at the secondary URI (i.e., a status callbackURI). The method is preferably implemented within a telephony platformsuch as the one described in U.S. patent application Ser. No.12/417,630, filed 2 Apr. 2009 and entitled “SYSTEM AND METHOD FORPROCESSING TELEPHONY SESSIONS”, which is hereby incorporated in itsentirety by this reference. The method may, however, alternatively beimplemented on any suitable system. The method is preferably used insystems that operate on a distributed system. For example, the telephonyplatform is preferably separate from the application server(s) hosting aspecific application. An application event may be an application error,a state change during a telephony session, a particular telephonyinstruction or user action, or any suitable event. An application errorcould occur in communication between the telephony platform and theapplication server(s). Alternatively, application error may be customererror such as when the application server sends improperly formed orillegal instructions to the telephony platform. State change of atelephony session may alternatively be an application event thattriggers communication with a status callback URI. The secondary URI maybe to a server operated by the same entity as the application server orit may be an outside third-party service or any suitable serverapplication. A status callback URI preferably does not alter the stateof the telephony session but can be used as a supplementary tool forproviding data to other services during a session. The method may beused for voice-based, short message service (SMS)-based, multimediamessaging service (MMS)-based, fax-based, or any suitable telephonynetwork based communication.

Step S110, which includes assigning a primary Uniform ResourceIdentifier (URI) and at least a secondary URI to an application,functions to specify a URI for handling typical telephony applicationhandling and a URI for handling a telephony application during acommunication failure. The primary and secondary URIs are preferablyuniversal resource locators (URL) that point to an application server orservers of the application operator. The primary URI and secondary URImay alternatively be any suitable address to resources of the telephonyapplication. The URIs may be set within a settings interface for anapplication administrator. The URIs may alternatively be resources on atelephony platform for a particular telephony application. Theseresources are preferably accessible through an application programminginterface (API) such as the API described in U.S. patent applicationSer. No. 12/417,630. The primary URI preferably includes a default valueof an initial URI. The initial URI is used for a new telephony session.This initial URI is preferably associated with an assigned telephonyaddress (e.g., a phone number, SMS long code, SMS short code, etc.) thatis used in determining what application server to manage a call. Forexample, when an incoming call is made to a phone number of anapplication, the initial URI associated with the phone number is used asthe primary URI for the first communication message sent to theapplication server. The primary URI is preferably updated during atelephony session during the communication with the application. Forexample, a telephony command may be sent to the telephony platforminstructing the telephony platform to gather the pressed digits during aphone call and to return the results to a new URI. The primary URI willpreferably change to the new URI after the results are gathered. At theend of a telephony session the primary URI is preferably reset to thedefault initial URI. The primary URI may alternatively remain unchangedfrom the initial URI. The secondary URI as described may be an addressto any suitable service. In one variation, the secondary URI is afallback URI that preferably addresses error handling code/logic. Thefallback URI is preferably hosted on a different application server incase the application server of the primary URI fails. In a secondvariation, the secondary URI is a status callback URI that preferablyaddresses a service that acts as a supplementary destination fortelephony session data as shown in FIG. 3. Status callback URIs may beused for sending transcripts, recordings, telephony session call flow,numbers dialed, and/or any suitable aspect of a telephony session. Astatus callback URI is preferably registered for particular type ofstate change in a telephony session such as the ending of a recording,but may alternatively be for a plurality of types of events such as thestart and end of any recording, transcription, and button input. Thesemay be registered for all instances of an application or be registeredduring a particular telephony session of an application. They may beregistered through telephony instructions, through an API, and/orthrough any suitable method. There may be a plurality of secondary URIs.One variation may allow specific errors or failures to be associatedwith specific fallback URIs. Another variation preferably uses multiplefallback URIs as redundant backups. For example, if after a primary URIfails a fallback URI is used, and if the fallback URI fails then thenext fallback URI is used. Additionally, multiple status callback URIsmay be used. A variety of third-party services may be used, each with astatus callback URI for different events of a telephony application.Status Callback URIs, and fallback URIs may additionally be used in thesame application, such that each application would be capable ofproviding status callbacks to various services and providing errorhandling code.

Step S120, which includes mapping a telephony session to the primaryURI, functions to enable a telephony session to be converted into aformat that may be handled with standard web servers and webapplications. The mapping is preferably performed using a call router.An initial URI (e.g., default primary URI) is preferably pre-specifiedat the call router by a web application (which may be running on a thirdparty server) or call router account owner. More preferably, the initialURI is assigned to the call via a unique identifier for the calldestination, such as a DID (Direct Inbound Dial) phone number, or a VOIPSIP address. The URI may alternatively be specified by a remote serveror other suitable device or method. In one variation, the URI may beused to encapsulate state information or a portion of state informationfrom the initiated telephony session, such as the originating phonenumber, the dialed phone number, the date and time of the call,geographic location of the caller (e.g. country, city, state, and/orzip), and/or the unique call ID. The information included in the URI maybe included in the form of a URI template. For example the URI defaulttemplate could be: http://demo.twilio.com/myapp/{dialed phonenumber}/{originating phone number} orhttp://demo.twilio.com/myapp/foo.php?dialed_number={dialed phonenumber}& originating_number={originating phone number}.

Step S130, which includes communicating with the application serverdesignated by the primary URI using an application layer protocol,functions to send and receive messages between the call router/telephonyplatform and the application server. The application control of atelephony session preferably occurs through the communication with theapplication server. The communication preferably includes the sending ofrequests to the application server; after the application serverprocesses the request, receiving a response; and processing theresponse.

Preferably, a telephony session request is sent to the primary URI.During the initial request sent to the application, the default initialURI is preferably used. The request is preferably sent to a server overa network. In one variation, the request is sent to a local server on alocal area network. In another variation, the request is sent to aserver running locally on the device originating the call. In yetanother variation, the request may be sent to multiple servers. Therequest preferably encapsulates at least a portion of the stateinformation from the initiated telephony session, such as theoriginating phone number, the dialed phone number, the date and time ofthe call, geographic location of the caller (e.g. country, city, and/orstate, zip), and/or the unique call ID. The request, more preferably,encapsulates all the state information of the call, but mayalternatively include no state information or partial state information.The state information from the initiated telephony session is preferablysent via HTTP POST in the request body, HTTP GET in the request URI,HTTP header parameters to mimic the data flow of a web browser, or byany combination or suitable alternative way. If new state information isgenerated in the course of the operation of the call router, a requestto the application server is preferably made to communicate the newstate and to request new telephony instructions. Preferably, new stateinformation is not kept or acted upon internally by the call router, butis passed to the application server for processing. Alternatively,partial state information is preferably stored on the call router untila fully updated state is achieved, and then communicated to theapplication server. For example, the application server may specify thatmultiple digits should be pressed on the keypad, not just one, beforenew call state is derived and communicated to the application server. Inone variation, the information from the initiated telephone session maybe a web-form submission included in the HTTP POST request. The requestmay include any state information from the telephony session, such asthe originating phone number, the dialed phone number, the date and timeof the call, and/or the unique call ID, the current status of the phonecall (pending, in-progress, completed, etc.), or the results of atelephony action, including Dual Tone Multi Frequency (DTMF) digitprocessing, or a representation of or a link to a sound recording, orthe status of the last command, or other call state. Examples of a HTTPGET request, a HTTP POST request, and a HTTP GET request are shown inFIGS. 4A, 4B, and 4C, respectively. Further examples of HTTPcommunication used for SMS messaging are shown in FIGS. 4D, 4E, and 4F.The HTTP request (or any suitable request communication) to the serverpreferably observes the principles of a RESTful design. RESTful isunderstood in this document to describe a Representational StateTransfer architecture as is known in the art. The RESTful HTTP requestsare preferably stateless, thus each message communicated from the callrouter to the application server preferably contains all necessaryinformation for operation of the application server and responsegeneration of the application server. The call router and/or theapplication server preferably do not need to remember or store previouscommunications to be aware of the state. Documents, media, andapplication state are preferably viewed as addressable resources,combined with data provide to the resource via request parameter, suchas HTTP GET or HTTP POST parameters, or request body contents. Suchrequest data may include an updated representation of the call resource,or other call state data generated as a result of call router operation,such as digits pressed on the keypad or audio recordings generated.State information included with each request may include a unique callidentifier, call status data such as whether the call is in-progress orcompleted, the caller ID of the caller, the phone number called,geographic data about the callers, and/or any suitable data. However, avarying level of a RESTful communication (statelessness) may be used,such as by using cookies, session tracking, or any suitable devices tosimulate a normal website visitor model. Preferably, data sent with eachrequest may fully enable the application server to determine the nextstate of the call to execute. RESTfulness preferably does not precludeusing external datasource, such as a database, to lookup additional datato log call meta data, or determine application logic.

The application server will preferably process the request and send aresponse to the call router. Thus Step S130 would include receiving aresponse from the application server. This response is preferably anHTTP response. The response is preferably sent as XML, audio binary, orraw text, but may alternatively be any sort of messaging format,including HTML, delimited text, key/value text or binary encoded format.The HTTP response preferably includes directions to perform telephonyactions. The response may alternatively or additionally include a newURI or a new URI template to use as the primary URI with the telephonyaction in Step S140. An additional example XML response is shown inFIGS. 5A and 5B.

Step S140, which includes receiving telephony instructions from theapplication server and processing the telephony instructions with thecall router, functions to convert the server response into telephonyactions or executable operations during a telephony session. Thetelephony actions may include, for example, playing a pre-recorded soundfile at a server-specified URI (such as a static mp3 file located athttp://demo.twilio.com/myapp/1234.mp3), reading text to the caller usingtext-to-speech technology, calling another number (such as creating anew voice connection through the PSTN, SIP/VoIP, or other IP technologysystem), collecting digits via DTMF input, recording voice responseaudio, TTY or other inputs, sending an SMS message, or any suitablecombination or sequence of these or other suitable actions. Thisconversion of the server response is preferably performed at a callrouter. Preferably, Step S120 includes processing the responsemime-types associated with the server response. For example, if theresponse mime-type is XML, it is considered to be a set of call routerinstructions. If the response mime-type is MP3, it is considered a soundfile to be played for the caller. If the response type is plain text, itis considered to be text to be read, via Text-To-Speech, to the caller.

Contents of the server response, such as an XML document, are preferablyconverted into a telephony action by processing the documentsequentially (e.g. line by line). Telephony instructions are preferablycontained within the document in the form of a markup language, such asXML as shown in FIGS. 5A and 5B. This sequential approach to processinga document of telephony instructions is enabled when the communicationis stateless and all the necessary information is contained within theURI. This stateless communication preferably allows telephonyinstructions (verbs or commands) to be used as the programming interfacefor a server application performing telephony services. Algorithmicinterpretation (based on the state of the communication) of thetelephony verbs or the document is preferably not necessary. Thetelephony actions are preferably executed in the order of telephonyinstructions found in the contents of the server response. For example,an XML document may include the necessary verbs to carry out thetelephony actions of reading text to a caller, monitoring keys pressedby the caller, and redirecting the caller to a new URI (i.e., an updatedprimary URI) using the pressed keys as part of the data within the newURI. Preferably, the telephony action (such as digits pressed) resultsin new state information, which may result in a repetition of some stepsof the method, preferably beginning at Steps S120 or S130. The next URIis preferably provided by the server as part of the processinginstructions. In another variation, the last URI is reused if the serverfails to specify a next URI. In yet another variation, no repetitionoccurs if the server fails to specify a next URI, and processingcontinues below at the next call router instruction. The behavior may bedetermined by the nature of the call router instruction; for example,instructions that generate no new state information would not need tohave a next URI since they don't trigger communication with a remoteserver. New state information may trigger an application event for thestate change of the telephony session. A secondary URI and morespecifically a status callback URI is preferably registered for a typeof state change such as recording beginning or recording end. When asecondary URI is registered for a particular state change, then thatstate change will be detected in Step S150. The telephony actionspreferably result in the repetition of step S130 with the new URIresulting from Step S140, but may alternatively initiate a repetition ofone or more steps of the method. Step S130 is preferably repeated usingall new phone session state information resulting from execution of atelephony action, such as digits pressed, a recorded audio file, or thesuccess or failure of any telephony action requested. Repetition alsoincludes all state information that remains relevant during the courseof the session, such as Caller, Called, unique Call ID, and call status.The state information may also be represented in the form of a URITemplate. For example, if the server response specifies that the callrouter should collect DTMF digits, and specifies that the next URL isthe URI Template http://demo.twilio.com/foo.php?digits={Digits}, and thecaller presses 1234. the resulting URI ishttp://demo.twilio.com/foo.php?digits=1234. Similarly, if the serverresponse specifies the URI Template:http://demo.twilio.com/myapp/{Digits}.mp3, the resulting HTTP Requestcould be to a static mp3 file located at:http://demo.twilio.com/myapp/1234.mp3. Thus, a call may be controlled byone server that issued the telephony instruction and a second serverthat processes the response. Such call control hand-offs constitute thetransfer of state information between servers in the form of a URI andaccompanying request data, such as GET, POST, and/or request body.Preferably, all state communications conform to a syntax established bythe call router to facilitate integration between multiple servers. Forexample, digits pressed on the keypad are preferably communicated toapplication servers in an identical fashion, thus minimizing the needfor coordination between a multiple application servers with regard tohow state is transferred. Alternatively, call router instructions maydictate the method of communicating new state information, such as thenames and types of variables to send representing new state.

Step S150, which includes detecting an application event, functions toidentify a trigger for use of a secondary URI. The application event maybe an application error, a state change during a telephony session suchas a particular telephony instruction or user action, or any suitableevent. Detecting an application error functions to determine if thecommunication for a telephony application has encountered failure orfatal error. In one variation, the application error is a communicationerror. A communication error is preferably an inability to properlycommunicate with the application server. This may occur if theapplication server is not operating as shown in FIG. 2A. When the callrouter is attempting to send a request to the application serverspecified by the primary URI, a server error message is returnedindicating a communication error has occurred. As another variation, theapplication error may be customer error. Customer error is an error inthe operation of the telephony application due to malformed or impropermessages from the application server as shown in FIG. 2B. This willcommonly include syntax errors in the code of the application server.They may respond to a request with invalid or unparsable instructions.Other application errors may be any suitable error that occurs in atelephony application. The application event may alternatively be astate change such as a state change during a telephony session, aparticular telephony instruction or user action, and/or any suitableevent. State changes may include the start, end or changes in telephonysessions for transcripts, recordings, telephony session call flow,numbers dialed, buttons pressed, and/or any suitable aspect of atelephony session. A status callback URI may be registered for aparticular type of event such as the ending of a recording, but mayalternatively be for a plurality of types of events such as the startand end of any recording, transcription, and button input. Such eventsare preferably detected during the execution of the telephonyinstructions as described above, from user input, or through anysuitable indicator of the state change.

Step S160, which includes communicating with the application serverdesignated by the secondary URI upon application event, functions to usethe secondary URI for handling aspects of the event. When applicationevent triggers a secondary URI that is a fallback URI, the communicationis preferably intended to handle an application error. When thesecondary URI is a status callback URI, data related to the event ispreferably sent to the service specified by the status callback URI. Asmentioned above a plurality of secondary URIs may be assigned for anapplication. There may be a plurality of fallback URIs and/or aplurality of status callback URIs.

A fallback URI may be used to catch errors and recover or to gracefullyinform a user in the telephony session of an error. Information aboutthe telephony session is preferably included in the communication withthe application server designated by the secondary URI. In onevariation, the request last sent to the application server is preferablyresent to the application server of the secondary URI. This willpreferably include the same HTTP parameters, and may additionallyinclude HTTP errors. Similar to how state is embedded in communicationusing the primary URI, state of the application at the time of theapplication error may be embedded in the secondary URI. The request mayencapsulate at least a portion of the state information from theinitiated telephony session, such as the originating phone number, thedialed phone number, the date and time of the call, geographic locationof the caller (e.g. country, city, and/or state, zip), and/or the uniquecall ID. The request, more preferably, encapsulates all the stateinformation of the call, but may alternatively include no stateinformation or partial state information. The state information from theinitiated telephony session is preferably sent via HTTP POST in therequest body, HTTP GET in the request URI, HTTP header parameters tomimic the data flow of a web browser, or by any combination or suitablealternative way. Using the state information an application server maybe capable of recovering the application state and proceed withoutending a telephony session or starting over. In this variation, thefallback URI may result in communication that updates the primary URI.Or in other words, the telephony application may recover and continuewith normal operation. Alternatively, a notification of the error maysimply be sent to the secondary URI and a static response (e.g., anaudio message informing user of the error) may be generically returnedand played to the user before ending the call.

In the case of the communication error, the secondary URI is preferablyhosted on a different server than that of the primary URI. The server ofthe secondary URI will ideally be operating even if the server of theprimary URI stops operating. The server of the secondary URI may includea mirror or duplicate instance of the server of the primary URI. Thuswhen a communication error occurs control of the application may bemoved over to the server of the secondary URI and proceed with normaloperation from the perspective of the user without ending the telephonysession.

In the case of customer error, the application server has providedmalformed or improper messages from the application server or theapplication server has caused the telephony platform to halt executionof the telephony application. Similar to the communication error, thestate information may be used to recover. However, the state informationmay alternatively be logged and used by the application developer inresolving errors in the application. Additionally, if the secondary URIfails another secondary URI may be used. Alternatively, a default errorhandling routine may be used within the telephony session. For example,a default message of the telephony platform may be played.

In the case of a state change application event, a telephonyinstruction, user action, or other indicator of the state changepreferably has an associated status callback URI. Data associated withthe state change is preferably communicated to an application serverspecified by the status callback URI. This status callback server may beoperated by the same entity as the main application server, but mayalternatively be operated by a third-party. The status callback serverpreferably receives the data and performs any suitable action. A replyis preferably not part of the communication, but continued communicationbetween the telephony platform (e.g., call router) and the statuscallback server may occur. Preferably, the communication. In thisvariation, the telephony session is preferably uninterrupted, and thecommunication with the application server of the secondary URI (e.g.,the status callback URI) happens in parallel to the communication withthe application server of the primary URI. Some exemplary applicationsof a status callback URI would be to send data relating to audiorecordings, transcriptions, telephony session call flow, numbers dialed,and/or any suitable aspect of a telephony session to a secondapplication.

An alternative embodiment preferably implements the above methods in acomputer-readable medium storing computer-readable instructions. Theinstructions are preferably executed by computer-executable componentspreferably integrated with a telephony platform preferably with a callrouter to mediate communication between telephony devices and anapplication server. The computer-readable medium may be stored on anysuitable computer readable media such as RAMs, ROMs, flash memory,EEPROMs, optical devices (CD or DVD), hard drives, floppy drives, or anysuitable device. The computer-executable component is preferably aprocessor but the instructions may alternatively or additionally beexecuted by any suitable dedicated hardware device.

As a person skilled in the art will recognize from the previous detaileddescription and from the figures and claims, modifications and changescan be made to the preferred embodiments of the invention withoutdeparting from the scope of this invention defined in the followingclaims.

We claim:
 1. A method for processing a communication session comprising:assigning a primary application resource identifier and at least astatus application resource identifier to an application; mapping acommunication session to the application; communicating with anapplication server designated by the primary application resourceidentifier using an application layer protocol, wherein communicatingwith the application server comprises embedding at least a portion ofstate information of the communication session in a first applicationlayer protocol request, sending the first request through an applicationlayer protocol to an application resource identified by the primaryapplication resource identifier, and receiving application instructionsin an application server response; processing the applicationinstructions into actions in the communication session; and upon anapplication status change event of the communication session, embeddingat least a portion of state information of the communication session andthe application event in a second application layer protocol request andsending the second request through an application layer protocol to anapplication resource identified by status application resourceidentifier.
 2. The method of claim 1, wherein the application statuschange is during the communication session.
 3. The method of claim 2,wherein sending the second request through an application layer protocolto the application resource identified by the status applicationresource identifier is performed in parallel to processing theapplication instructions into actions.
 4. The method of claim 3, whereinembedding at least a portion of state information of the communicationsession and the application event in a second application layer protocolrequest comprises embedding at least a portion of state information atthe time of the application status change in the second applicationlayer protocol request.
 5. The method of claim 1, wherein theapplication status change is the end of the communication session. 6.The method of claim 1, further comprising updating the primaryapplication resource identifier during the communication session.
 7. Themethod of claim 1, wherein processing the application instructions intoactions in the communication session comprises transmitting acommunication message.
 8. The method of claim 7, wherein thecommunication message is a short message service (SMS) message.
 9. Themethod of claim 1, wherein processing the application instructions intoactions in the communication session comprises calling a secondendpoint.
 10. The method of claim 1, wherein the status applicationresource identifier may be registered for a plurality of types of statechanges in a communication session.
 11. The method of claim 1, furthercomprising creating call router resources accessible through a callrouter Application Programming Interface (API), wherein the primaryapplication resource identifier and the status application resourceidentifier are call router resources.
 12. The method of claim 1, furthercomprising assigning an error application resource identifier to anerror event of the application; upon the error event occurring in thecommunication session, embedding at least a portion of state informationof the communication session and an error identifier in a thirdapplication layer protocol request and sending the third request throughan application layer protocol to an application resource identified bythe error application resource identifier.
 13. A method for processing acommunication session comprising: assigning a primary applicationresource identifier and at least an error application resourceidentifier to an application; mapping a communication session to theapplication; communicating with an application server designated by theprimary application resource identifier using an application layerprotocol, wherein communicating with the application server comprisesembedding at least a portion of state information of the communicationsession in a first application layer protocol request, sending the firstrequest through an application layer protocol to an application resourceidentified by the primary application resource identifier, and receivingapplication instructions in an application server response; processingthe application instructions into actions in the communication session;and upon an application error while processing the applicationinstructions, embedding at least a portion of state information of thecommunication session from the time of the application error and anerror identifier in a second application layer protocol request andsending the second request through an application layer protocol to anapplication resource identified by the error application resourceidentifier.
 14. The method of claim 13, further comprising receiving aresponse to the second request, wherein the response to the secondrequest includes a second set of instructions; and processing the secondset of instructions into actions in the communication session.
 15. Themethod of claim 14, wherein processing the second set of instructionsinto actions of the session comprises updating the primary URI of thesession.
 16. The method of claim 13, further comprising upon applicationerror in communication with the secondary application identifier, usinga default error handling routine within the communication session. 17.The method of claim 13, wherein the application error is a communicationerror when communicating with the application server designated by theprimary URI.
 18. The method of claim 13, wherein the application erroris customer error of invalid application instructions in the firstapplication layer protocol response.
 19. The method of claim 13, furthercomprising initiating the communication session from a phone numberthrough the Public Switched Telephone Network (PSTN).
 20. The method ofclaim 13, further comprising initiating the communication session from amessage received from a Short Message Service (SMS) system.
 21. Themethod of claim 13, further comprising creating call router resourcesaccessible through a call router Application Programming Interface(API), wherein the primary application resource identifier and errorapplication resource identifier are call router resources.